In one such known device (Swiss patent specification No. 502 151) the cooling medium supply ring is rigidly mounted on the boring tool. In cases where boring tools of various different working diameters are provided, it is always of the same diameter. In each case, the same coupling head can be fitted axially over the cooling medium supply ring, this coupling head having a cylindrical bore the diameter of which corresponds to the outside diameter of the cooling medium supply ring and the wall surface of which forms the first sealing surface. The outer surface of the cooling medium supply ring forms the second sealing surface. When the boring tool is interchanged with another boring tool, the coupling head is withdrawn axially from the previously used boring tool and pushed over the new boring tool. In the case of machines with which a plurality of like holes are bored one after another, no serious problems arise.
At the present time, however, it is not uncommon for a number of mechining operations to be carried out one after the other on the same workpiece using various different tools on universal machine tools which are usually referred to as "machining centers." In such a machining center, a plurality of tools are fed in succession from an external tool magazine, by means of a conveying device, to the working spindle and are also conveyed back again from the latter, the interchange of the tools being effected automatically. Very few of the machining centers which are in use at present, however are provided with a cooling medium supply means whereby the rotating cutting tool could be supplied with the cooling medium through the drive spindle. The fitting of rotary cutting tools of the kind initially referred to, which are provided with a cooling medium supply ring, would give rise to difficulties in the case of machining centers, since this cannot be done automatically because of the necessary feed tubes. The previously known device for the supply of cooling medium that was referred to initially is also unsuitable for such machining centers, since the removal and axial mounting of the coupling head for each successive tool would be time-consuming and would require complicated operating mechanisms.
Devices for supplying cooling medium to boring tools are also known in which the cooling medium supply ring is rotatably mounted on the shank of the boring tool. The cooling medium supply ring is in addition held against axial displacement by two spring rings, which engage in annular grooves formed in the tool shank, one in front of and one behind the cooling medium supply ring. In this case, the cooling medium supply ring has a radial base in which the coupling head connected to the supply pipe can be inserted and retained by a spring clip. Even in this case difficulties are encountered in machining centres when the tools are frequently changed, since the insertion of the coupling head into the radial bore and the fixing thereof in the bore cannot be carried out fully automatically by simple means.
The problem that lies at the root of the invention is to provide an arrangement for supplying a cooling medium to rotary metal-machining cutting tools, particularly for boring tools of the kind initially referred to which, even with machining centers, enables a cooling medium to be suplied to the cutting tools via a cooling medium supply ring, in which the cooling medium supply ring is automatically connected to the coupling head without the aid of additional operating mechanisms after the cutting tool has been fitted and is also automatically disconnected during tool changing. The arrangement according to the invention will also be suitable in addition for subsequent incorporation in already existing machining centres.